Reducing Air Pollution
Goldman noted that there are a variety of considerations to take into account when reducing air pollution, specifically, levels of ozone, particulate matter, volatile organic compounds, nitrous and sulfur oxides, and metals like mercury. For example, policy makers should consider how fuels burn, and whether one fuel is cleaner than another. “We add fuel oxygenates to motor vehicle fuels to increase octane and make them burn more cleanly, and ethanol has substituted for MTBE (methyl tertiary-butyl ether) and some of the other oxygenates,” she said.
Second, she noted that diesel fuel combustion creates a great deal of air pollution. The U.S. Environmental Protection Agency (EPA) and other regulatory authorities have sought to develop cleaner diesel fuel, and biodiesel has been thought to be a pathway to development of cleaner alternatives.
Third, she identified the problem of indoor air pollution from burning biomass fuels for household heating and cooking. Such fuels are very dangerous in terms of the pollution they produce indoors. Alternative fuels that burn more cleanly could replace the biomass fuels or could be used to generate electricity for households thus reducing exposures within the home environment.
At the same time, Goldman said, it is important to take into account the life-cycle effects of the various potential energy sources. Thus, when considering air pollution levels, it is important to take into account not only the air pollution that is generated by fuel combustion, but also the air emissions that occur across the entire life-cycle of growing the plants, producing the fuels, and transporting the fuels. Unfortunately, she said, “that is not generally how we perform risk assessment.”
Reducing Greenhouse Gases
A second major policy goal is reducing air pollutants that act as greenhouse gases. “We know that global climate change already is having a profound impact on the public’s health,” Goldman said. However, as Timothy D. Searchinger, Princeton University, pointed out in his talk, it now seems that some of the early assessments of the potential of biofuels to reduce greenhouse gasses were overly optimistic, largely they did not take into account land-use changes.
She asserted that although it was once thought that biofuels would play a significant role in efforts to reduce greenhouse gases, no clear